Inlays and Onlays
 

What is the Procedure for an Inlay?

As with any treatment, an examination or consultation is required. The dentist first needs to look at the tooth in question and discuss the different treatment options with you.

When considering an inlay or onlay, an X-ray is needed to check the following things:

  • Has it been root filled? If yes, the success of this must also be assessed.
Note. If a tooth has had a root canal, then it is generally best restored by a full coverage crown
(A full coverage inlay/onlay is a viable alternative.)
  • Are there any signs of infection around the end of the root indicating the tooth needs a root canal treatment?
  • How does the periodontal support of the tooth look?
  • What is the extent of the decay, if there is any? Is the tooth restorable? If the decay or caries extends deep under the gum, the tooth may not be able to be saved and need an extraction
  • How close it gets to the nerve chamber is also important in predicting future problems and deciding whether or not to perform a root canal. Special tests will also help in determining the most appropriate treatment.


The actual procedure for an inlay/onlay takes two appointments unless a CEREC machine is being used to fabricate it, whilst you are in the chair. The first appointment to prepare the tooth tends to take a little longer (about an hour) than the second appointment (to cement it in).

Appointment 1

The process is very similar to the procedure for having a crown, it usually involves the following stages:

  • Numbing the tooth that is to be restored (giving local anaesthetic).
  • Taking impressions of the opposing set of teeth so the lab can get the bite right.
  • Taking an impression of the tooth in question- often patched with a little filling or wax to restore the shape of the tooth for making a temporary later.
  • Removing any decay and existing filling to get down to natural tooth and then shaping the remaining cavity so the dentist can easily take an impression of it. It is important not to have any undercuts, so the restoration can easily be cemented or bonded- in. The dentist will also remove any weak pieces of tooth to prevent the possibility of fracture in that area in the future.
  • Taking a final impression of the cavity on which the lab will make your inlay. This is a crucial step as it is on this model, that they will make the inlay/onlay. The material used is often a silicone, which can take a number of minutes to set (longer than the impression for the opposing model), because it is much more accurate. The dentist will need to check that the impression has recorded every detail accurately and if not, the process will need to be repeated until a suitable impression is recorded.
  • The dentist then needs to record how you bring your teeth together by taking a bite registration. Often this is a fast- setting silicone material that is squirted onto your teeth. Then you bite together and keep your mouth closed until it has set. Biting into a piece of wax is another way, and if you have a lot of teeth and a predictable, consistent bite when you close together, that might be all the lab needs.
  • Making a temporary. This can be made using the impression taken before the tooth was prepared. It uses a self-cure acrylic, which is inserted into the impression, then reseated inside the mouth and left to harden slightly, before it is removed and polished. This would then be cemented in place with a temporary (weak) cement. There are other types of temporary material available some of which are simply pushed into the tooth, shaped and set (it depends on the dentist's preferences). The temporary is important, as it stops the tooth from being sensitive and maintains the bite and space between the next tooth- so the final restoration will fit nicely.
  • The bite is then checked to ensure that it is not too high; you are then cleaned up and after a rinse- good to go.

Appointment 2

This takes 30 to 60 minutes depending on the dentist and generally involves the following:

  • Most of the time, the tooth will need to made numb again, as it is likely to be sensitive after the temporary is removed. Unless the tooth has had root canal therapy.
  • The temporary is removed, often using a combination of a scaler and a bit of pressure from a hand instrument to flick it out. In some instances the temporary may need to be drilled out, if the cavity shape was very retentive.
  • The tooth is then thoroughly cleaned, washed and dried to remove the temporary cement.
  • The dentist will then try out the inlay/onlay and check the fit and contact with the neighbouring teeth. If it is too tight, it might require a bit of adjustment until it sits down properly. On rare occasions, the fit may be sufficiently different for a new impression and a re-make to be needed.
  • The actual procedure for placing the restoration will differ depending on the type of inlay/onlay material and the dentist's choice of cement or bond. It may involve one simple step and set chemically or require curing with the 'special blue dental light'. Other materials have multiple steps and involve preparing the tooth and the inside of the porcelain and then bonding them together. Whatever the technique, it is very important that the area remains dry and is not contaminated with saliva. For this reason it may be done under rubber dam (a protective latex sheet), or by padding you out with dry tips and cotton wool rolls and a salivary ejector.
  • The dentist must ensure that floss can be passed through the contacts and that all excess cement material has been removed.
  • Finally the bite will be adjusted so it feels comfortable and all your other teeth should be meeting normally.